Wind power installation with separate primary and secondary cooling circuits

ABSTRACT

A wind power installation includes a nacelle, and energy conversion system for converting wind power into electric energy. The energy conversion system includes a heat-generating source which is disposed in the nacelle and constructed to include a closed primary cooling system using air for dissipating generated heat. Further provided is an open secondary cooling system which uses ambient air for cooling heated air from the primary cooling system.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a division of prior filed copending U.S. applicationSer. No. 11/042,836, filed Jan. 24, 2005, which in turn is acontinuation of prior filed PCT International application no.PCT/DE2003/002355, filed Jul. 11, 2003, which designated the UnitedStates and on which priority is claimed under 35 U.S.C. §120, and whichclaims the priority of German Patent Application, Serial No. 102 33947.3, filed Jul. 25, 2002, pursuant to 35 U.S.C. 119(a)-(d).

BACKGROUND OF THE INVENTION

The present invention relates, in general, to a wind power plant, andmore particularly to a wind power installation of a type having agenerator disposed in a nacelle and including a cooling circuit, and aturbine with at least one rotor blade.

Nothing in the following discussion of the state of the art is to beconstrued as an admission of prior art.

Typically, a wind power plant has a rotor blade which is rotatablearound a horizontal axis and pivotable around a vertical axis to turnthe rotor blade in appropriate alignment to the wind. The rotor blade isrotated by wind velocity at speed depending on diameter and shape of therotor blade and its pitch to drive a generator, so that wind power isconverted into electric energy. The conversion of energy normallyresults in energy loss in the form of heat. This heat loss applies inboth the conversion of kinetic energy of wind into electric energy inthe generator of a wind power plant as well for the electrical feedingof energy, generated by the wind power plant, into an electric powersupply network. This heat loss takes place also in other electricalcomponents, in particular the electronic power equipments, such as e.g.inverter or transformer. Also other components of the wind power plantheat up such as gears, bearings or control units like, e.g., hydraulicsystems or similar control and regulation units, which adjust the rotorblades or turn the wind power plant towards the wind.

The heat loss amounts hereby to 5 to 7% of the installed nominal output.Heretofore, the heat loss has been dissipated into the environment byusing fans which pull in cold air from outside to cool the correspondingcomponent, e.g., the generator. The heated air is then discharged againto the outside. This is disadvantageous especially when the outside airis humid or has a high salt content particularly in coastal regions, andthe components to be cooled are then exposed to this humid and saltyair.

German patent publication no. DE 198 02 574 A1 describes a wind powerinstallation having a generator which is cooled by an air streamproduced by low pressure at a mouth of a rotor blade. This low pressureresults in a pressure drop between each mouth of a rotor blade and anopening on a rotor blade distal side of the nacelle. As a consequence,ambient air is drawn in at the opening in opposition to the actual winddirection and flows via the flow path through the nacelle and throughthe interior of a rotor blade toward the mouth of this rotor blade. Theprovision of such a closed circulating ventilation is disadvantageousand, especially when located off-shore, results air with high saltcontent being aspirated. Moreover, noise is generated by the mouths atthe rotor blades.

German patent publication no. DE 199 47 915 A1 describes a coolingsystem for cooling heat-generating structures in particular of a windpower plant, using a chimney effect of heated air to cool the structuresin the foot region of the tower and also in a top area of the nacelle.It is hereby disadvantageous that the tower cross section is alreadyformed with channels. Moreover, also a closed circulating ventilationsystem is involved here which is susceptible to penetration of dirt andhumidity and thus is unsuitable for carrying out a reliable operation.

U.S. patent publication no. 2001/0035651 describes a wind powergenerating device in which lost energy of the generator is dissipated tothe ambient air by direct heat conduction to the outer skin of thenacelle which is provided with ribs for surface enlargement. Thiscooling system is however able to dissipate only little heat energy.

It would therefore be desirable and advantageous to provide an improvedwind power installation which obviates prior art shortcomings and isreliable in operation even for off-shore operation, without experiencingbreakdown or maintenance works as a result of contaminated or saltycooling air.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a wind powerinstallation includes a nacelle, energy conversion means for convertingwind power into electric energy, said energy conversion means includinga heat-generating source disposed in the nacelle and constructed toinclude a closed primary cooling system using air for dissipatinggenerated heat, and an open secondary cooling system using ambient airfor cooling heated air from the primary cooling system.

It will be appreciated by persons skilled in the art that cooling bymeans of the primary cooling circuit should not be limited to thegenerator only but also includes other electrical equipments such asconverters or slip-ring members of the generator.

By separating the primary cooling circuit from the secondary coolingcircuit, a wind power installation in accordance with the presentinvention can be erected at any site, irrespective of adverse outerconditions. In other words, the wind power installation can also bebuilt offshore where humid and salty air is prevalent because theprimary cooling circuit is encapsulated or enclosed internally and asufficient cooling action of the nacelle can be realized using the wind.The air velocity about the nacelle is dependent on wind strength,whereby the relationship between wind strength and generator output andthus also generator losses is proportional.

Suitably, the nacelle is constructed as secondary air cooler so as torealize an air-air cooler.

According to another feature of the present invention, the secondary aircooler may be constructed in the form of a heat exchanger which isdesigned as tube bundle and secured to the nacelle or forming part ofthe nacelle. Suitably, the tube bundle is disposed in an upper portionabout the nacelle. Heated air produced by the generator or otherelectrical components connected to the primary cooling circuit rises oris forced by fans into the interstices between the tube bundles andcooled there by wind flowing through the tube bundles. The cooled air ofthe primary cooling circuit is flowed back through natural convection orby a further fan for cooling the generator or other electricalcomponents disposed in the nacelle. The arrangement of the tube bundleon the nacelle ensures an alignment of the tubes of the tube bundle inparallel relationship to a wind direction so as to provide a sufficientcooling action by wind velocities and sufficient passage of air throughthe tube bundle. The tube bundle forms the heat exchanger between theprimary and secondary circuits.

To provide a particularly efficient heat transfer, the tubes may beformed with surface-enlarging structures.

According to another feature of the present invention, the secondarycooler has an inlet and an outlet, wherein the inlet or the outlet ofthe secondary cooler is disposed on the nacelle at a location which hasenhanced flow dynamics.

According to another feature of the present invention, air of theprimary cooling circuit exits the nacelle via tubes. Suitably, thenacelle may be constructed such as to resemble a handle-shaped objectwhen viewed in wind direction. Accordingly, the primary cooling circuitmay have at least one handle-shaped tubular member on the nacelle, withambient air, i.e. wind, freely flowing about the handle-shaped tubularmember and defining the secondary cooling circuit. Suitably, the tubeshave at least one outlet provided in the upper portion of the nacelle,and at least one inlet preferably disposed in the lower portion of thenacelle so as to enable a natural convection of air of the primarycooling circuit. To assist the natural convection, fans, in particularaxial fans, may be provided.

According to another feature of the present invention, the tubularmember may have a first port, disposed in an upper portion of thenacelle for receiving heated air from the heat-generating source, and asecond port, disposed at a location below the outlet, for returningcooled air into the nacelle. Suitably, a fan may be provided forassisting a circulation of air through the tubular member

Compared with facilities operating with air-water cooling systems, awind power installation according to the present invention has theadvantage of being compact, substantially maintenance-free and reliableoperation, without any need for preparing coolants in great amounts. Asa result, costs are low. Compared to wind power plants with closedcirculating ventilation in particular of the generators, a wind powerinstallation according to the present invention is less likely tobreakdown as a result of humid or salty air.

The outgoing heated air of the primary cooling circuit can be used toheat the nacelle, rotor blades, in particular during the cold season.Condensate formations on electrical equipment and ice build up on therotor blades are thereby eliminated.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be morereadily apparent upon reading the following description of currentlypreferred exemplified embodiments of the invention with reference to theaccompanying drawing, in which:

FIG. 1 is a longitudinal section of one embodiment of a wind powerinstallation according to the present invention;

FIG. 2 is a cross section of the wind power installation of FIG. 1;

FIG. 3 is a longitudinal section of another embodiment of a wind powerinstallation according to the present invention; and

FIG. 4 is a cross section of the wind power installation of FIG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the Figures, same or corresponding elements are generallyindicated by same reference numerals. These depicted embodiments are tobe understood as illustrative of the invention and not as limiting inany way. It should also be understood that the drawings are notnecessarily to scale and that the embodiments are sometimes illustratedby graphic symbols, phantom lines, diagrammatic representations andfragmentary views. In certain instances, details which are not necessaryfor an understanding of the present invention or which render otherdetails difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to FIG. 1, there is showna longitudinal section of one embodiment of a wind power installationaccording to the present invention, including a nacelle 2 which issupported by an unillustrated tower. The nacelle 2 supports at least onerotor blade which is rotatable around a horizontal axis by wind velocityto drive a generator, so that wind power is converted into electricenergy. Besides the generator, the nacelle 2 accommodates also otherheat-generating electrical components, e.g. converter or slip-ringmember of the generator. For sake of simplicity, reference numeral 1 isused in FIG. 1 to generally indicate a heat-generating source 1.Although not shown in detail, the generator as heat source 1 has alaminated stator core and laminated rotor core, whereby the laminationsof the stator and/or the rotor are traversed in a manner known per se byradial and/or axial ventilation channels defining a closed primarycooling circuit. Furthermore, the air of the primary cooling circuit mayflow through the air gap of the generator.

The nacelle 2 further accommodates above the heat source 1 a system oftube bundles 6. Currently preferred is the arrangement of the system oftube bundles 6 upon the top surface of the nacelle 2. Wind for drivingthe rotor blade on the nacelle 2 flows through the tube bundles 6 inaxial direction and enters the system of tube bundles 6 via an inlet, asindicated by arrow 4, and exits the tube bundles 6 through outlet, asindicated by arrow 5 to thereby define an open secondary coolingcircuit. The tube bundles 6 act as heat exchanger between the inlet 4and outlet 5 to transfer heat from air, circulating in the closedprimary cooling circuit of the heat source 1, to wind sweeping throughthe system of tube bundles 6. The heated air from the heat source 1enters the system of tube bundles 6 via an outlet 7, is cooled there andflowed back through convection and/or a fan 8 to the heat source 1.Reference numeral 10 designates the transition zones between the primarycooling circuit and the secondary cooling circuit realized by the heatexchanger in the form of tube bundles 6.

FIG. 2 shows a cross section of the wind power installation and depictsin more detail the arrangement of the tube bundles 6 in the nacelle 2.The tubes of the tube bundles 6 have a cylindrical configuration and aresuitably formed with unillustrated surface-enlarging structures toenhance the cooling efficiency. Examples of such surface-enlargingstructures may include ribs or fins. The nacelle 2 is constructed forrotational movement to properly align the rotor blade or blades of thewind power installation in relation to the wind direction and thus toenable an alignment of the tube bundles 6 in axis-parallel relationshipto the wind direction. As a result, the air throughput through the tubebundles 6 is increased and the cooling efficiency is improved.

Referring now to FIG. 3, there is shown a longitudinal section ofanother embodiment of a wind power installation according to the presentinvention. Parts corresponding with those in FIG. 1 are denoted byidentical reference numerals and not explained again. The descriptionbelow will center on the differences between the embodiments. In thisembodiment, the outlet 7 of the primary cooling circuit is constructedin the form of a handle-shaped, tubular member 9 (see FIG. 4) whichprojects from the outlet 7 to an area outside the nacelle 2 and isreturned for connection to the primary cooling circuit of the heatsource 1 via an inlet 3. The heat transfer of the primary cooing circuittakes also place by natural convection and/or fan 8. The tubular members9 may be assembled on site from single parts.

FIG. 4 shows a cross section of the wind power installation of FIG. 3and depicts in detail the basic arrangement of the tube system of theprimary cooling circuit of the heat source 1 with its tubes extending inwind direction and suitably formed with surface-enlarging structures(not shown). The convection of heated air in the primary cooling circuitcan be facilitated by disposing the outlet 7 in the upper portion of thenacelle 2 and by disposing the inlet 3 below the outlet 7 in midsectionor lower portion of the nacelle 2.

A wind power installation according to the present invention has thefollowing advantages: There is no need for an intermediate watercircuit, including of the air-water cooler of the generator. Theprovision of an air-air cooler outside the heat source 1 allows thecreation of more space in the tight nacelle 2. Operation issignificantly safer compared to conventional systems while at the sametime maintenance work can be reduced. There is no need for a coolingwater supply and for a cooling water preparation and supervision. Theenergy consumption of the secondary devices such as, e.g., water pumpsor monitoring devices, is reduced. The heated air of the primary coolingcircuit may also be used to heat the nacelle 2 or even the rotor bladesso as to prevent problems relating to ice buildup during the cold wintermonths. Suitably, fans are hereby provided to realize a proper aircirculation.

Compared to wind power installations with closed circulatingventilation, the wind power installation according to the presentinvention is also safer to operate as no humid air or salty air isconducted into the operating space of the electrical components orequipments.

While the invention has been illustrated and described in connectionwith currently preferred embodiments shown and described in detail, itis not intended to be limited to the details shown since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention. The embodiments werechosen and described in order to best explain the principles of theinvention and practical application to thereby enable a person skilledin the art to best utilize the invention and various embodiments withvarious modifications as are suited to the particular use contemplated.

1. A wind power installation, comprising: a nacelle; energy conversionmeans for converting wind power into electric energy, said energyconversion means including a heat-generating source disposed in thenacelle and constructed to include a closed primary cooling system usingair for dissipating generated heat; and an open secondary cooling systemusing ambient air for cooling heated air from the primary coolingsystem.
 2. The wind power installation of claim 1, wherein the secondarycooling system is thermally coupled to the primary cooling system. 3.The wind power installation of claim 1, wherein the secondary coolingsystem is constructed in the form of a tube bundle received in thenacelle and having tubes aligned in parallel relationship to a winddirection.
 4. The wind power installation of claim 1, wherein theprimary cooling circuit includes a handle-shaped tubular member whichextends to an area outside the nacelle, with the secondary coolingsystem being realized by freely flowing ambient air.
 5. The wind powerinstallation of claim 4, wherein the tubular member has a first port,disposed in an upper portion of the nacelle for receiving heated airfrom the heat-generating source, and a second port, disposed at alocation below the outlet, for returning cooled air into the nacelle. 6.The wind power installation of claim 4, and further comprising a fan forassisting a circulation of air through the tubular member.